Pointing Device Inertial Isolation and Alignment Mounting System

ABSTRACT

An inertial isolation and alignment system for a sensitive component or apparatus affixed to a mortar barrel comprising a barrel clamp assembly which supports two parallel bearing rail followers and pointing device cage assembly which supports two parallel linear bearing rails. The bearing rail followers and linear bearing rails form a simple sliding contact linear motion bearing system. The bearing rail followers on the barrel clamp assembly allow the cage assembly to slide freely along the length of the linear bearing rails. During firing, the travel vector is decoupled from the cage assembly by the bearing rail followers as they move with the barrel along the linear bearing rails leaving the cage assembly suspended in inertial space. The cage assembly then accelerates under the force of gravity over the distance of the displaced travel of the bearing rail followers back to its rest position landing on dampers, each on a linear bearing rail.

RELATED APPLICATIONS

The present patent application claims priority under 35 U.S.C. § 119(e)to U.S. Provisional Patent Application Ser. No. 60/793,169, which wasfiled Apr. 19, 2006. The full disclosure of U.S. Provisional PatentApplication Ser. No. 60/793,169 is incorporated herein by reference.

FIELD

This invention relates to large bore weapons and more particularly to amethod and apparatus for isolating a shock from a mortar firing eventwhile maintaining the alignment of a sensitive electronic pointingdevice for use on a mortar barrel or similar device.

BACKGROUND

During the firing of a large bore weapon a significant reaction force isimparted to the barrel and support structure. A support structure, whichis required to travel a certain distance before absorbing the load,allows the barrel and its attached components to undergo a nearlyinstantaneous high-g acceleration. Sensitive electronic pointingdevices, such as inertial measurement units (IMUs) or inertialnavigation systems (INSs), and their attachment structures have beendestroyed by this extreme acceleration and deceleration on occasion.

The present invention is a method and apparatus for isolating asensitive electronic device from the barrel recoil travel using a linearmotion bearing mounting system. For example, Honeywell's TacticalAdvanced Land Inertial Navigator (TALIN™) pointing device requires amortar mount assembly designed to provide a stable and protective cageparallel to the center line of the barrel. The mortar barrel of a 120 mmmortar weapon moves approximately twelve inches (12″) under a highacceleration, developing energy of approximately five hundred thousandfoot-pounds (500 k ft-lbs.) and then decelerates to a stop in less than0.010 seconds when fired from a base plate in a free standingconfiguration. More particularly, this mount needs to provide for therepeated firing of the mortar weapon without realignment or mechanicaladjustment while maintaining a zero ballistic force vector on thepointing device.

Presently, typical PDMAs (pointing device mounting assemblies) cannotwithstand the recoil acceleration force while attached to a 120 mmmortar barrel when fired. The typical PDMA experiences catastrophicfailure of the steel mounting plates due to stress in excess of thebending moment of the material of their construction. This force exceedsthe PDMA shock isolators' travel limit and transfers the shock load intothe RLG (ring laser gyroscope) pointing device, causing internalphysical damage.

Others have tried to solve the problem by designing a mounting platformfor the RLG pointing device which allows the mortar barrel to recoilwhile separating the RLG pointing device from the recoil force through ashaft and sleeve bearing assembly. There is still hammer shock with thisdesign, however, due to the loosely coupled parts. This design alsolacks the durability desired for a PDMA.

A prior art device, described in U.S. Pat. No. 4,336,917, uses gasdriven pistons and gas accumulator/controllers that aresensor-controlled to maintain position during shock and vibration.Another prior art device, described in U.S. Pat. No. 6,814,179, usesshock isolators that are comprised of rubber and polyurethane foam toabsorb shock and vibration.

SUMMARY

The present invention solves the problem of inertial isolation byproviding a mechanical assembly designed to provide a linear travelsupport frame constructed of bearing rail followers aligned parallelwith the barrel reactive force vector and suspending the mass of thepointing device on linear bearing rails in a cage assembly that providesand maintains alignment while allowing the mortar weapon to accelerateand decelerate without transfer of motion to the suspended pointingdevice. The pointing device then returns to its rest position on thelinear bearing mounting system by gravitational force. The parts worktogether to isolate the acceleration vector of the mortar barrel fromthe TALIN™ mass. During firing, the mortar barrel moves the attachedbearing rail followers along the linear bearing rails, without impartingany acceleration to the cage assembly containing the TALIN™. Thecombined linear bearing rails and bearing rail followers form a simplesliding contact linear motion bearing system. During the mortar firingrecoil, the force vector loads are directionally decoupled between thebearing rail followers and the linear bearing rails in their axis oftravel. This prevents the mass of the RLG pointing device frominertially loading the cage assembly in excess of its out of planedeflection limits.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described herein with reference to the followingdrawings. Certain aspects of the drawings are depicted in a simplifiedway for reason of clarity. Not all alternatives and options are shown inthe drawings and, therefore, the invention is not limited in scope tothe content of the drawings. In the drawings:

FIG. 1 is a perspective view of the preferred inertial isolation andalignment assembly mounted on a mortar weapon;

FIG. 2 is a perspective view of the preferred inertial isolation andalignment assembly of FIG. 1 in the extended position;

FIG. 3 is a perspective view of the preferred inertial isolation andalignment assembly of FIG. 1 in the ready-to-fire position;

FIGS. 4A and 4B are front and side views of the preferred barrel clampassembly; FIGS. 5A and 5B are front and side views of the preferred cageassembly;

FIG. 6 shows the preferred inertial isolation and alignment assembly inthe pre-fire condition; and

FIG. 7 shows the preferred inertial isolation and alignment assemblyimmediately after a firing condition.

DETAILED DESCRIPTION

Disclosed is a preferred embodiment of an inertial isolation andalignment assembly 100 for mounting a sensitive component such as apointing device to a mortar weapon, or the like. FIG. 1 shows aperspective view of inertial isolation and alignment assembly 100,affixed to a mortar weapon comprising a base plate 110, mortar barrel120, and bipod 130. The inertial isolation and alignment assembly 100 isaffixed to the underside of mortar barrel 120. As can be seen, inertialisolation and alignment assembly 100 consists of a barrel clamp assembly200 to secure inertial isolation and alignment assembly 100 to mortarbarrel 120, and a cage assembly 300 to encase a pointing device 310,such as a TALIN™ pointing device.

FIG. 2 depicts a perspective view of the preferred inertial isolationand alignment assembly 100 in the extended position. The first part ofthis embodiment is barrel clamp assembly 200 which mounts to mortarbarrel 120. Barrel clamp assembly 200 includes bearing rail followers210, which position linear bearing rails 340 parallel to mortar barrel120. The second part of this embodiment is cage assembly 300, whichencases pointing device 310 and anchors linear bearing rails 340. Thetop surface 212 and bottom surface 214 of bearing rail followers 210, incombination with the linear bearing rails 340, form the basis of thesliding contact linear motion bearing system, similar to the slideactions of semi-automatic rifles or pistols.

FIG. 3 shows a perspective view of the preferred inertial isolation andalignment assembly 100 of FIG. 1 in the ready-to-fire position. Itillustrates how linear bearing rails 340 of cage assembly 300 slidethrough bearing rail followers 210 of barrel clamp assembly 200,effecting the simple sliding contact linear motion bearing system.

FIG. 4A shows a front view of the preferred barrel clamp assembly 200.Barrel clamp assembly 200 comprises a saddle structure 220 and a saddleclamp structure 230 with saddle clamp bolts 240. Saddle structure 220has saddle extensions 222 with bearing rail followers 210. Saddlestructure 220 and saddle extensions 222 form a one piece “C” channelstructure. However, saddle extensions 222 could also be separatemounting blocks permanently affixed to saddle structure 220. Saddleclamp structure 230 is affixed to saddle extensions 222 with saddleclamp bolts 240. Saddle extensions 222 are drilled and tapped from thetop side at each corner to receive saddle clamp bolts 240. This entiresaddle structure 220 is preferably machined from a solid piece of barstock (such as 4340 steel, for example) to provide uniform strength andstress distribution throughout the structure. Saddle structure 220 canalso be manufactured from aluminum, titanium, plastic, composite, orother materials able to withstand the forces exerted by a particularmortar weapon, and the temperature rise of the mortar barrel experiencedduring firing.

Barrel clamp assembly 200 is subjected to the acceleration and firingshock of more than two thousand g's on the 120 mm mortar weapon duringfiring. This shock, coupled with torsional stress from a bolt down forceof more than 95 foot-pounds across the diagonal length of barrel clampassembly 200 and the temperature rise from repeated firings, requiresadditional structure for the barrel clamp assembly 200 to remaindimensionally stable.

FIG. 4B shows a side view of the preferred barrel clamp assembly 200.Saddle clamp structure 230 comprises two semi-circular shaped bands 232with gusseted bolt eye extensions 234, which fit over mortar barrel 120and bolt on both sides of saddle structure 220. Saddle clamp structure230 also comprises a rigid mechanical connection 236, connecting the twosaddle clamp bands 232, in order to assist in holding the alignment ofinertial isolation and alignment assembly 100 constant. Rigid mechanicalconnection 236 can also function as a handle. The entire saddle clampstructure 230 is preferably machined from a solid piece of bar stock(such as 4340 steel, for example) to provide uniform strength and stressdistribution throughout the structure. Saddle clamp structure 230 canalso be manufactured from aluminum, titanium, plastic, composite, orother materials able to withstand the forces exerted by a particularmortar weapon, and temperature rise of the mortar barrel experiencedduring firing. Rigid mechanical connection 236 and saddle clamp bands232 of the saddle clamp structure 230 can be three separate piecesbolted together, as long as the assembly maintains rigidity.

FIG. 5A shows a front view of the preferred cage assembly 300. The cageassembly 300 comprises side plates 320, base structure 330, linearbearing rails 340, shock isolators 350, and shock dampers 360. Basestructure 330 comprises two side members 332, which are bolted to a basemember 334 to form a u-shaped shelf for mounting pointing device 310.Side plates 320 are fastened to shock isolators 350. Shock isolators 350are also fastened to side members 332 of base structure 330. Basestructure 330, shock isolators 350, and side plates 320 form anopen-ended box for encasing pointing device 310. Linear bearing rails340 are fastened to side plates 320, and shock dampers 360 are fastenedto the front ends of linear bearing rails 340. Pointing device 310 isbolted onto base member 334 of base plate 330.

Shock isolators 350 reduce the parallel and cross-axis firing shock onthe pointing device during a firing event. The quantity and type ofshock isolators 350 used is determined by the firing shock responsespectrum from a particular mortar weapon and the spectral frequenciesand magnitudes of attenuation required by the isolated mass. Shockisolators 350 are axially aligned with the center-of-mass of pointingdevice 310.

Shock dampers 360 are placed on the front ends of linear bearing rails340. Shock dampers 360 provide reduced g-loads on the suspended pointingdevice cage assembly 300 as it returns to its rest position after afiring event. Shock dampers 360 may consist of air or hydraulic pistons.Shock dampers 360 may alternatively consist of springs or rubbermaterial.

FIG. 5B is a side view of the preferred cage assembly 300. Fasteners 322connect side plates 320 to linear bearing rails 340. The fasteners 322are preferably cap head socket screws, but are not limited to this typeof fastener. Although FIG. 5B shows eight fasteners 322 attaching eachof the linear bearing rails 340 to each of the side plates 320, thisinvention is not limited to eight fasteners, and other numbers offasteners may be used.

The length of linear bearing rails 340 is determined by the maximumamount of linear travel expected by the mortar barrel 120 during afiring event. In the case of the 120 mm mortar weapon, the typicaltravel distance required to seat the base plate in soft soil isapproximately 12 inches, therefore the length of guide rails for thisapplication would be approximately 20 inches.

FIG. 6 depicts the inertial isolation and alignment assembly 100 mountedon the underside of mortar barrel 120 while the mortar weapon is at restprior to the initial firing. The initial installation of inertialisolation and alignment assembly 100 is accomplished by bolting saddleclamp structure 230 to saddle structure 220 around mortar barrel 120using saddle clamp bolts 240. Saddle clamp bolts 240 are tightened to apredetermined torque limit, such as 95 ft-lbs. for the 120 mm mortarweapon, in a sequential pattern at 10 ft-lb. increments. Followingproper installation of barrel clamp assembly 200 around mortar barrel120, cage assembly 300 is installed by aligning linear bearing rails 340with bearing rail followers 210, and sliding cage assembly 300 towardthe base plate until it is resting on shock dampers 360, as shown inFIG. 6. This is the ready-to-fire position.

FIG. 7 depicts the extended position of the inertial isolation andalignment assembly 100. During a firing event, mortar barrel 120 recoilstoward the base plate, causing barrel clamp assembly 200 to slide alonglinear bearing rails 340 of the inertial isolation and alignmentassembly 100. At the end of the firing event, mortar barrel 120 comes toa stop, leaving cage assembly 300 suspended on linear bearing rails 340at a point equal to the distance the mortar barrel traveled duringfiring, as shown in FIG. 7. This is the extended position. The force ofgravity then causes cage assembly 300 to slide down toward the baseplate, and come to rest on the shock dampers 360 to the ready-to-fireposition depicted in FIG. 6. This operation is repeated as many times asis required by the firing of the mortar weapon.

As described above, cage assembly 300 is quickly installed by aligninglinear bearing rails 340 with bearing rail followers 210 and slidingcage assembly 300 to the ready-to-fire position where it is resting onshock dampers 360. For the quick disconnect, the process is simplyreversed. Cage assembly 300 is removed by sliding it from theready-to-fire position beyond the extended position, until linearbearing rails 340 become free of bearing rail followers 210.

Although the invention has been described in detail with particularreference to a preferred embodiment, other embodiments can achieve thesame results. Variations and modifications of the present invention willbe obvious to those skilled in the art and it is intended to cover inthe appended claims all such modifications and equivalents. The entiredisclosures of all references, applications, patents, and publicationscited above, are hereby incorporated by reference.

1. An inertial isolation and alignment assembly for aligning andisolating a shock of a sensitive component affixed to a barrel, theinertial isolation and alignment assembly comprising: a saddle clampstructure configured to removably affix the inertial isolation andalignment assembly to the barrel; a cage assembly affixed to the saddleclamp structure and configured to encase the sensitive component; and alinear motion bearing system comprising at least two linear bearingrails and at least two bearing rail followers, wherein the linearbearing rails and bearing rail followers cooperate to inertially isolatethe cage assembly from the saddle structure, and wherein the at leasttwo linear bearing rails are anchored to the cage assembly.
 2. Theinertial isolation and alignment assembly of claim 1, wherein the saddleclamp structure comprises clamps.
 3. The inertial isolation andalignment of claim 1, wherein each of the at least two bearing railfollowers is configured to accept a respective one of the at least twolinear bearing rails to form a sliding contact linear motion bearingsystem.
 4. The inertial isolation and alignment assembly of claim 1,wherein each of the at least two bearing rail followers is configured toaccept a respective one of the at least two linear bearing rails so thateach of the at least two linear bearing rails is substantially parallelto the mortar barrel.
 5. (canceled)
 6. The inertial isolation andalignment assembly of claim 1, further comprising shock dampers disposedat an end of each of the at least two linear bearing rails.
 7. Theinertial isolation and alignment assembly of claim 1, further comprisinga quick release mechanism for the cage assembly.
 8. A method forisolating a shock of a sensitive component affixed to a mortar barrelusing an inertial isolation and alignment assembly, wherein the inertialisolation and alignment assembly comprises a saddle clamp structureconfigured to removably affix the inertial isolation and alignmentassembly to the mortar barrel, a cage assembly affixed to the saddleclamp structure and configured to encase the sensitive component, and alinear motion bearing system, wherein the linear motion bearing systemcomprises at least two linear bearing rails and at least two bearingrail followers, wherein the linear bearing rails and bearing railfollowers cooperate to inertially isolate the cage assembly from thesaddle structure, and wherein the at least two linear bearing rails areanchored to the cage assembly, the method comprising: sliding the atleast two linear bearing rails through the at least two bearing railfollowers when a projectile is fired through the mortar barrel, therebycausing the cage assembly to be suspended in inertial space; anddampening a fall of the cage assembly.
 9. The method of claim 8, themethod further comprising affixing a saddle structure that contains theat least two bearing rail followers to the mortar barrel.
 10. The methodof claim 8, wherein each of the at least two bearing rail followers isconfigured to accept a respective one of the at least two linear bearingrails.
 11. The method of claim 8, the method further comprisingproviding that the at least two linear bearing rails are substantiallyparallel to the mortar barrel.
 12. The method of claim 8 whereindampening comprises providing shock dampers.
 13. The method of claim 8,the method further comprising releasing the cage assembly from thesaddle structure when dismounting the sensitive component.